Will this work? Guest House Feed

[david5253]

3400 SF house on a slab, nearby guest house fed by a 90amp subpanel. Need to supply power in the GH for the heat and lights in a power outage. We have a home standby generator with an automatic transfer switch. Transfer switch has an available 2 pole 30 amp breaker to feed an interlock kit and breaker on the subpanel. I have an existing circuit under the slab which is no longer being used(its 10-2 w/g). Can I tie into this via a junction box and send it to the guest house subpanel (through an existing conduit) where it will use the neutral in the panel to supply 120 volt circuits? The grounds and neutral are isolated.

Thanks in advance for your help!

 

[wyliesdiesels]

3400 SF house on a slab, nearby guest house fed by a 90amp subpanel. Need to supply power in the GH for the heat and lights in a power outage. We have a home standby generator with an automatic transfer switch. Transfer switch has an available 2 pole 30 amp breaker to feed an interlock kit and breaker on the subpanel. I have an existing circuit under the slab which is no longer being used(its 10-2 w/g). Can I tie into this via a junction box and send it to the guest house subpanel (through an existing conduit) where it will use the neutral in the panel to supply 120 volt circuits? The grounds and neutral are isolated.

Thanks in advance for your help!

where is the ATS located? on the main house? if so, why do you need a separate feed for backup power?

no you cannot do that with a shared neutral. all the circuit conductors need to be together for a number of reasons.

furthermore if the 10/2 is NM-b, its not rated for underground use and should be abandoned.

if you have a useable conduit why not just pull the required conductors?

 

[mm08822]

Where is the 90a cb getting its power from and where relative to the transfer switch?

Why involve a 2nd feed when you can use the 90a feeder?

10-2 rx adds too much complexity and not straight forward.

 

[david5253]

The ATS is located in the main house but currently does not feed anything for the GH. That's why I want to provide power via the ATS.

You said I can't have a shared neutral and the wires have to all be together for a number of reasons - what are those reasons? Could I just run a separate neutral from the ATS and tie it in with the underground feeder 10-2 W/G?

The wires under the slab are UF rated. I would be using the conduit but it only starts where the UF comes out of the slab.

The main panel feeds a subpanel in the detached garage and that panel feeds the GH. But the easiest way to get power to the GH panel is by tying into the ATS at the main house.

If I am able to run a new 10-3 W/G from the ATS to the GH panel through an interlock kit, would that be ok?

 

[PCustoms]

Does the ATS cover the whole house? If so, why is the guest house no covered?

Does the guest house have its own panel?

How far is the GH?

 

[david5253]

The ATS does not cover the whole house, only selected circuits. In the winter months we need to provide power for the GH heater. The GH does have its own panel and is located about 12' away from the main house, the ATS is about 90' from the GH panel. There is an available conduit between the main house and the GH.

 

[mm08822]

Using the existing 10-2 or even changing out to 10-3, you are creating multiple paths for the neutral and grd to the GH. And this assumes that a gen interlock is installed the the GH panel. I assume the GH panel has a main.

Upgrading the xfer switch to a whole house version is the cleanest, safest, most convenient way .

 

[wyliesdiesels]

The ATS does not cover the whole house, only selected circuits. In the winter months we need to provide power for the GH heater. The GH does have its own panel and is located about 12' away from the main house, the ATS is about 90' from the GH panel. There is an available conduit between the main house and the GH.

i would just connect the GH feeder to the ATS and be done with it. lot easier than the route you plan to take